Electromagnetically operated hand tool



July l0, 1955 A. M. MaoFARLAND 2,753,898

ELECTROMAGNETICALLY OPERATED HAND TOOL.

Filed May', 1950 2 Sheets-Sheet 1 /E' 4 fyi IN VEN TOR.

July 10, 1956 A. M. MaCr-'ARLAND 2,753,898

ELECTROMAGNETICALLY OPERATED HAND TOOL Filed May 5 1950 2 Sheets-Sheet 2 United States Patent O ELECTRMAGNEHCALLY OPERATED HAND TOOL Allison M. MacFarland, Cleveland, Ohio Application May 3, 1950, Serial No. 159,794

9 Claims. (Cl. 14S- 73) This invention relates to reciprocative tools, and more particularly to electrically operated hand reciprocative tools.

The present invention provides an improved reciprocative tool which is operated by an electromagnet actuated by alternating current. More specifically, the tool of the present invention is adapted for manual operation as contrasted with fixed installations. Tools of this type are particularly adapted for use by amateur tool operators and the tool to be described hereinafter is particularly suitable for such use. An inherent disadvantage of electromagnetically actuated tools is the tendency of the structure carrying the tool to stall at the ends of the reciprocating stroke and particularly at the end of the stroke adjacent the electromagnet. This is caused by the inertia of the tool structure and in part by the residual magnetism which remains in the magnetic materials surrounding and associated with the electromagnet even after the current in the electromagnet has dropped to zero. The present invention contemplates providing means to offset or compensate for these factors and thereby overcome and substantially eliminate the tendency of the tool to stall.

ln hand tools of the type set forth above it is often desirable to provide a steady guide for the work piece or for the tool so that a neater job can be performed using the tool, lt also is desirable at times to be able to place the tool upon a supporting surface thereby to permit both of the hands of the user to be free to guide the work around the tool.

An important object of the present invention is to provide in a tool of the type described an improved tool carrying structure; more particularly there is provided a tool carrying structure which is pivotally mounted on its supporting structure.

Another object of the invention is to provide a tool structure of the type described including means to eliminate the tendency of the tool to stall at the end of the stroke adjacent the electromagnet.

A further object of the invention is to provide a tool of the type described which provides a longer and more powerful stroke for the tool.

Still another object is to provide in a tool of the type described an improved means for controlling the length of the tool stroke.

Yet another object is to provide in a tool of the type described an improved detachable guide and support table.

Still another object is to provide in a tool of the type set forth an improved detachable structure for supporting the tool upon a supporting surface thereby to free both hands of the user for guiding the work piece about the tool.

A still further object is to provide a tool of the type described which is more convenient, durable and simple in operation and which is simple and economical in construction.

These and other advantages of the invention will be 2,753,898 Patented July 10, 1956 ice apparent from the following specification, when taken in connection with the accompanying drawings wherein a preferred embodiment has been set forth for purposes of illustration.

In the drawings wherein like reference numerals are used to refer to like parts throughout:

Figure l is a side elevational view of a tool made in accordance with and embodying the principles of the present invention;

Figure 2 is an end View of the tool shown in Figure 1;

Figure 3 is an enlarged partial view in cross section of the tool shown in Figure 1 substantially as seen in the direction of the arrows along the line 3 3 thereof;

Figure 4 is an enlarged View in cross section of the lefthand portion of the tool shown in Figure 1 and illustrating particularly the structure of the electromagnet and its associated switch;

Figure 5 is a view in cross section of the stroke regulating means substantially as seen in the direction of the arrows along the line 5 5 of Figure 4;

Figure 6 is a side view similar to Figure l showing a detachable work supporting table made in accordance with the present invention mounted on a tool embodying the principles of the present invention, the table being shown in cross section;

Figure 7 is an end view of the tool end supporting table shown in Figure 6;

Figure 8 is an enlarged cross sectional View substantially as seen in the direction of the arrows along the line 8-8 of Figure 6 of the support structure which mounts the supporting table on the tool;

Figure 9 is a View similar to Figure 6 showing the tool provided with leg members for supporting the tool in operative position upon a supporting surface; and

Figure 10 is an end view of the tool shown in Figure 9.

Referring to the drawings, and particularly to Figure 1 thereof, there is shown a tool, generally designated by the numeral 10, made in accordance with and embodying the principles of the present invention. A saw has been shown for the purposes of illustration, but it is to be understood that the invention is applicable to other forms and types of tools.

The tool 10 comprises generally a body 12 upon which is mounted an electromagnet 14, a handle 16 and a U-shaped frame 18. The body 12 is provided at its lefthand end, as viewed in Figure 1, with a pair of downwardly extending supporting members 20 and 21 at the free end of which are formed clamps 22 and 24, respectively (see Figure 2) which clampingly engage the handle 16 therebetween. A bolt 26 passes through the clamp members 22 and 24 and is provided with a nut 28 which cooperates with bolt 26 to hold the clamping members 22 and 24 in clamping engagement about handle 16. Another portion of body 12 in cooperation with sections of sheet metal attached thereto forms the core 30 of electromagnet 14. Wire 32 is wrapped about and within the core 30 to provide the necessary current-carrying conductor, the ends of wire 32 extending downwardly through the bottom of electromagnet 14 as at 34 and 36. The switch mechanism which connects electromagnet 14 to a suitable source of alternating current will be described more fully hereinafter.

The righthand end of body 12 as viewed in Figure l has attached thereto a pair of spaced apart support members 38 and 39 on which is mounted the U-shaped frame 18. The U-shaped frame 1S includes an upper arm 4l), a lower arm 42 and a rounded bight portion 44 which interconnects arms 40 and 42. The connection between the U-shaped frame 18 and body portion 38 is made at a point below the center of bight portion 44. Frame the free end thereof.

current in the coil 32 -has dropped to zero.

-reciprocative stroke.

`whenthe current in the electromagnet drops to zero. is'to befnoted that auxiliary spring 80 ceases to act as 18 is disposed between the support member 38-39 and is pivotally connected thereto by means of a shaft 46 which interconnects the support members Sli-39. This structure allows free pivotal .movement of frameY 1S about shaft 46 within .limits imposed by the presence of structures to be described hereinafter.

The free outer ends of arms 40 and 42 of frame 18 are adatped to receive and carry a tool such as the saw blade 48 Lower 'arm 42 is preferably provided with a notch as at 50 which receives a projection 52 on blade 48. The upper arm 40 is vadapted to .receive a clamping member 54 which clamps this end of blade 48 to arm 40.in a secure manner.

Means is provided for resiliently holding U-shaped frame 18 in a fixed position with respect to body 12 in the form of a resilient leaf spring S6. Referring to AFigure 3 there is shown the manner in which one end of spring 56 is secured to body .12. A pair of brackets 53 .and 60, which are L-shaped in cross section, is attached to body 12 by any suitable means Vsuch as bolt 62 and nut 64. With vthe L-shaped brackets disposed as shown inFigure 3, portions 66 and 68 thereof are disposed away from each other and lie in a plane perpendicular to the lplane of frame 18. A clamping plate 70 serves to clamp `the'spring S6 against the upper edge of portions 66 and 68 whereby to rmly tix one end of spring 56 to body 12. Bolts 72 and 74 hold the clamping plate '70 in fixed assembled position with respect to brackets 5S and 60.

The other end of spring 56 is firmly attached to the lower arm 42 of frame 1S at a point spaced away from A pair of brackets' 76 .and 78 mounted on arm 42 serves to receives this end of spring 56.

As has been stated above, in tools of the type shown in the drawing the tool carrying frame 18 tends to stall at the end of the stroke adjacent -the electromagnet 14 dueto the residual magnetism -remaining in the magnetic materials forming the core of the electromagnet. This residual magnetism tends to hold the vframe 18 downwardly against the action of spring 56 even after the Means is provided in the form ofan auxiliary spring 8G to overcome this 'tendency to stall at the lower end of the Spring 80 is attached to brackets 76-78 vand-has one end thereof bent downwardly as at 82 toward body 12. 'End 82is so positioned as to contact body 12 at the end of the stroke adjacent the electromagnet whereby to be deformedvand thereby exert an additional force Atending to throw frame 18 upwardly It Vsoon as frame 18 has moved a short distance upwardly. Means is provided to var-y the length of the stroke ofrthe'frame 18 in the form of an eccentric cam 84.

kCam'84 is lixedly attached to the shaft 86 thatisrotatably mounted in aligned apertures formed in supporting members 20-21 and auxiliary-plates-88-90 which areassembled on the body `12 by any suitable fastening means such as rivet 92. As maybe best seen in Figure 5 one .-e'nd of `shaft-88 is provided with a circular knob A94 having indicia formed on the circumference thereof. The indicia are preferably positioned on knob 94 in such la manner that'the lowest number when .positioned upwardly corresponds to the shortest length of stroke for frame 18. Means is provided for retaining cam 84 in its set position in the. form of a spring 96 which is cornvention to energize and dcenergizc electromagnet 14. This switch, generally designated by thc numeral 98, comprises a pair of switch contacting members and 1452 which may be urged into contacting relationship by means of switch lever 194. The power line 106 has the usual two lead wires 1193 and 116, lead wire 163 being connected to one of the connections 36 to coil 32, and lead wire 110 being connected to the contacting member 1011. Connection 34 of coil 32 is attached to contacting member 102. Normally the contacting members and are held spaced apart whereby to interrupt the circuit connecting coil 32 to power line 165.

Switch lever 194 includes a hand gripping portion 112 which is pivotally supported on a iiber washer 114 encircling the upper end of handle 16. When lever 1114 is positioned to the right as seen in Figure 4, the contacting members 1041 and 162 are moved into contacting relationship whereby to energize coil 32 from power line 106. Upon release of lever 164 the contacting member 192 moves to the position shown due to the resilience thereof and breaks the circuit to coil 32, thereby deenergizing electromagnet 14.

Operation of tool 1t) is as follows. The operator places a suitable tool such as saw blade 43 across the open ends of frame 1S. After connecting power line 106 to a suitable source of potential the tool is grasped by handle 16 and one or more fingers placed over the switch lever 164. vWhen switch lever 114- is pressed inwardly electromagnet 14 is energized. The source of potential connected to power line 106 must be of the alternating type whereby to cause periodic reversals of the polarity of electromagnet 14. If the potential energizing line 166 is of the usual sixty cycle type, the electromagnet 14 will 'be energized and deenergized 12% times a second, that is,

times a second the electromagnet 14 will act .as a magnet of one polarity, -lose its magnetic properties, and assume magnetism of a reverse polarity as the current through coil 32 moves from zero value to maximum, returns to zero and rises again to a maximum.

As theV current increases through coil 32 the magnet formed by this coil and its associated magnetic core increases in strength, drawing the U-shaped frame downwardly, bending spring 56 across cam 84 and eventually compressing spring Si? against body 12. As the current falls to vZero in coil 32 the strength of the electromagnet drops rapidly, but as explained above the magnetic materials tend tomaintain their residual magnetism which produces stalling of the frame 13. However, the combined forces applied by springs 56 and S2 is suiiicient to overcome the force of attraction created by this residual magnetism and frame 13 is moved upwardly. The momentum or inertia of frame 18 will be sufficient to carry the frame past its neutral position as seen in Figure l and its upper movement is counteracted by the tension set up in -spring 56 as this spring is bent upwardly. The tension of spring 56 in conjunction with the next magnetizing cycle Vof electromagnet 14 serves to pull frame 18 downwardly whereby to repeat the cycle of operation described.

In certain applications it is desirable to make the frame v1S of some relatively light metal or metal alloy whereby to conserve energy and obtain more ecient operation of the tool. A preferred material of construction for frame 18 is an aluminum-magnesium alloy which possesses the desired characteristics of structural strength and light weight. Since such alloys are not magnetic in char- Y acter it is essential to make certain of the members attached thereto magnetic whereby to preserve the interaction between electromagnet 14 and frame 18. In such ngiveanjncreased electiveness to electromagnet 14. On

the other hand, handle 16, switch lever 104 and washer v114 are preferably made of non-conductive' materials such -as wood or liber. It is to be understood that the invention is not to be limited to these particular preferred materials but that other suitable materials having the necessary characteristics may be used.

There is shown in Figures 6, 7, and 8 a work piece lsupporting and guiding table detachably mounted on the lreciprocative tool described above and shown in Figures 1-5 of the drawings. Although the table has been shown applied to applicants improved tool, the table having .particular application on such a tool, it is to be underlstood that the table can be used on other portable hand ltools. The table 116 is a relatively thin and substantially Arectangularly shaped piece of material such as wood, j plastic, or light gauge metal. It is to be understood that Athe table maye be made of any other suitable material having the designed degree of rigidity whereby to give sup- 1 port and may be made in other shapes than the one described. An aperture 118 is provided near the forward -end of table 116 in such a position that the tool such as 'the saw blade 48 may extend therethrough and have clear- .ance therearound.

Means is provided for mounting the table 116 in the iform of two pairs of support members. The forward pair of support members 121) and 122, see Figure 7, are positioned to support the table 116 a short distance behind `the tool 48 and the rear support members 124 and 126, :see Figure 8, are positioned to support the rear edge tof the table 116. The upper ends of the support mernlbers 120, 122, 124, 126, are provided with laterally and youtwardly extending flanges 128, 130, 132, and 134 respectively. Any suitable fastening means such as the rivets 136 interconnect each of the laterally extending ilanges and the table 116. The upper ends of the fasteners 136 are formed flush with the upper surface of table 116 whereby to provide a smooth work piece supporting surface.

The front set of support members 12S-122 are detachably connected to the forward extending portion of core 30 by means of a bolt 138 which passes through a suitable aperture in core 30 and aligned apertures in support members 1Z0-122. A wing nut 140 or other snitable fastening element cooperates with bolt 138 clampingly to hold support members 12d- 122 on the core 3i).

The rear support members 124-126 are similarly attached to the body 12 near the center thereof. More specifically, aligned apertures formed in body 12, brackets 58-60, and the rear support members 124-126 receive a bolt 142 which in cooperation with a wing nut 144 clampingly holds these elements together. A spacer block 146 is disposed between support member 124 and bracket 5S and a similar spacer 148 is disposed between support member 126 and bracket 60.

The above described structure makes it possible to rapidly and easily attach the work table 116 to the tool or remove the work table from the tool. The support members for the table 116 are so constructed and arranged that they will not interfere with the proper operation of the tool such as the reciprocative saw blade By providing table 116 the tool can be more steadily and .easily guided on the work piece being shaped and particularly in those instances in which the outline of the Vwork piece is curved or otherwise complicated in shape. .Such a work table, however, does not interfere with the portability or ease of operation of the hand tool.

Referring now to Figures 9 and 10 there is shown another embodiment of the work table and its associated support members which adapt the tool for use when both hands of the operator are required to guide the work piece. More specifically, the form of the invention shown in Figures 9 and l0 provides support legs for resting the tools solidly upon a supporting surface. As may be beit seen in Figure 10, the front support members 126m ard. v122:1 are provided with legs 150 and 152 respectively which are formed as extensions of the support members 12M-122e. The legs 150 and 152 are spaced apart from each other by means of outwardly extending members 154 and 156 respectively. To give a greater degree of steadiness to the assembly, the legs and 152 are provided at the lower ends with outwardly extending tianges 158 and 160 respectively which give a broader base of support or contact with the supporting surface.

The rear support members 124e and 126e are provided with similar legs 162 (the leg attached to support member 124a not being shown in the drawing). Leg 162 is provided with an outwardly extending flange 164 to give added steadiness thereto. With the structures shown in Figures 9 and 10 the portable tool can be rested upon a supporting surface whereby to allow both hands of the user to be free to guide a work piece against the tool. This support structure, however, does not interfere with the portability of the tool and in addition is easily and quickly removed by disconnecting the bolts and wing nuts described above.

1t will be seen that there has been provided an electromagnetically operated tool which has the advantages and characteristics set forth above. More particularly, there has been provided an improved mounting for the tool carrying frame which gives more satisfactory and eicient operation and which gives a more desirable motion of the tool carried by the frame such as saw blade 48. Means has been provided in the form of spring Si) to overcome any tendency to stall at the lower end of the tool reciprocating cycle. ln addition, an improved means has been provided to control the length of the tool stroke. The device illustrated is essentially foolproof in operation, is simple and rugged in construction and may be economically fabricated.

Although a preferred embodiment of the invention has been shown for the purposes of illustration, it is to be understood that various changes and modifications may be made therein without departing from the spirit and scope of the invention. Accordingly, the invention is to be limited only as set forth in the following claims.

I claim:

l. An electrical reciprocative hand tool comprising a body, an electromagnet attached to said body, a tool carrying frame pivotally mounted on said body and positioned to be attracted by said electromagnet, resilient means holding said frame away from said electromaget whereby to impart a reciprocating stroke to said frame when said electromagnet is alternately energized and deenergized, and eccentrically shaped cam means rotatably mounted on said body and engaging said resilient means whereby to control the length of said stroke according to the angular position of said cam.

2. An electrical reciprocative hand tool comprising a body, an electromagnet attached to said body, a tool carrying frame pivotally mounted on said body and positioned to be attracted by said electromagnet, resilient means holding said frame away from said electromagnet whereby to impart a reciprocating stroke to said frame when said electromagnet is alternately energized and deenergized, and auxiliary spring means disposed between said frame and said body, said spring means being contacted and compressed when said frame is positioned toward said electromagnet near the end of the stroke, to urge said frame away from said electromagnet when said electromagnet is deenergized.

3. An electrical reciprocative hand tool comprising a body, an electromagnet attached to said body, a substantially rigid U-shaped frame of a relatively lightweight non-magnetic material pivotally mounted on said body, one arm of said frame being positioned adjacent said electromagnet, magnetic material means fixed on said one arm and in position to be attracted upon energization of said electromagnet, and leaf spring means holding said frame away from said electromagnet whereby to impart reciprocating motion to said frame when said electromagnet is alternately energized and deenergized, one

end of said leaf spring means being connected lwith said one arm of the frame and providing at least a portion of said magnetic material means.`

4. An electrical reciprocative hand tool comprising a body, an electromagnet attached to said body, a substantially U-shaped frame pivotally mounted on said body, one arm of said frame being position adjacent said electromagnet and in position to `be attracted thereby upon energization of said electromagnet, spring means holding said frame away from said electromagnet, said frame being adapted 4to partake of reciprocative motion when said electromagnet is alternately energized and deenergized, and an auxiliary spring attached to said one arm adapted to be contacted and compressed when said frame draws near said electromagnet whereby Vto impart an additional force urging said frame away from said electromagnet.

5. An electrical reciprocative hand vtool comprising a body, an electromagnet attached to said body, a substantially U-shaped frame pivotally mounted on said body, one arm of said frame overlying said electromagnet and positioned to be attracted thereby Yupon energization of said electromagnet, spring means interconnecting said body and said frame and adapted to hold said frame spaced away from said electromagnet, said frame being adapted to partake of reciprocating motion when said electromagnet is alternately energized and deenergized, an eccentrically shaped cam mounted on said frame and underlying'and contacting said spring means, and handle means for rotating said cam means whereby `to position said frame nearer and farther away from said electromagnet upon turning said cam whereby to vary the length of the stroke of said frame.

6. An electrical reciprocative hand tool comprising a body, handle means for manually supporting said body, an -electromagnet attached to said body, a substantially VU-shaped -frame pivotally mounted lon said body, one arm of said frame being positioned adjacent said electromagnet, spring'means interconnecting said frame and said body and holding said frame away from said electromagnet, means positioned -between said body andsaid spring 'means for varying the distance between said frame and said electromagnet whereby to vary the lengthof the stroke of said frame when said electromagnet is alternately energized and deenergized, and auxiliary spring vmeans Vfastened to said frame and adapted to `be compressed when said -frame approaches near said electromagnet whereby to impart -an additional force tending to move said frame away from said electromagnet when-said electromagnet is deenergized.

7. An electrical reciprocative hand tool comprising a body, handle means for manually supporting'said body, an electromagnet attached to said body, a substantially U-shaped frame pivotally mounted on said body, ,one

arm of said frame being positioned adjacent said .electromagnet, spring means interconnecting said frame and said body'and holding said `frame away from said elec: tromagnet, and means positioned between said body and said spring means for varying the ,distance between said frame and said velectromagnet whereby t0 vary the length of the stroke of said frame when said electromagnet is alternately energized and deenergized.

8. An electrical reciprocative hand tool comprising a body, an electromagnet attached to said body, a substantiall;l U-shaped frame pivotally mounted on said body, one arm of said frame being positioned adjacent said electromagnet and in position to be attracted thereby upon .energization of said electromagnet, spring means holding said frame away from said electromagnet, said frame being adapted to partake of reciprocative motion when said electromagnet is alternately energized and deenergized, and a leaf spring attached at one end thereof to said one arm and positioned between said one arm and said electromagnet, the other end of said spring being bent toward .said electromagnet and positioned a short distance therefrom when the electromagnet is deenergized, said spring being adapted to .be contacted by said body and' compressed thereagainst when said frame approaches said electromagnet whereby to impart an additional force urging said frame away from said electromagnet.

9. An electrical reciprocative hand tool, comprising a body, an electromagnet attached to said body, a tool carrying kframe mounted on said body and positioned to be attracted by said magnet, resilient means yieldably holding said frame away from said electromagnet for imparting a reciprocating stroke to said frame when the electromagnet is alternately energized and deenergized, and additional resilient means operable when the frame is drawn `to the `electromagnet for yieldably urging said frame means away from the electromagnet when the electromagnet Vis deenergized and during the initialportion ofthe frame movement awayfrom the electromagnet.

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